What is the lowest you run you lipo down to

[davethepitch]

I have been reading a few forums and it appears some people have different views on what the lowest level you should run your lipo';s down to and some say 3.3v others say 3.6v to 3.7v (gives time to land) and a few said 3.0v but that does not leave much landing time.

What are your views and then i will look for either a common denominator or take an average voltage to work from.

Dave

[JT]

3.6 is good, your lipo';s will stay in good condition for much longer, they don';t like being drained too far too often

[Friskle]

Anyone saying 3.0v well, they must be happy buying batteries on a regular basis, and even 3.3v is cutting things very fine, every battery i use usually comes of at 3.785 per cell.

[Beaver2206]

3.6v is where I am happy to take it down to, though usually try not to go down too close to that level

[davethepitch]

3.6 is good, your lipo';s will stay in good condition for much longer, they don';t like being drained too far too often

Hi JT

I was hoping folk would say around 3.6v to 3.7v as i want to set my low voltage alarm for my lipo';s but was unsure what value to set it at.

[JT]

3.6v is the way to go Dave Had many of my lipos for 1-2 years and they are still pretty good

[davethepitch]

3.6v is the way to go Dave Had many of my lipos for 1-2 years and they are still pretty good

I have already set the alarm to 3.6v 

[ched]

Great thread Dave.
On my first flights I left my lipo alarm set as supplied at 3.2v. As soon as I got continuous tone I landed. I have 2 x Turnigy 2200mAh 25C and 3 x Zippy 1800mAh 25C all 3S.
the rested voltage on the Turnigy 2200mAh =  10.4v (3.46 ave cell) but on  the Zippy 1800mAh = 10.9v (3.63 ave cell)
the Charger (X120) put back in Turnigy 2200mAh = 2180mAh (1760= 80%)  but on  the Zippy 1800mAh = 1550mAh (1440 = 80%).

OK so the charge put back in is actually the total the charger used and it';s not 100% efficient, well I hope that';s how it works?

Second flight session lipo alarm = 3.4:
the rested voltage on the Turnigy 2200mAh =  10.8v (3.6 ave cell) but on  the Zippy 1800mAh = 11.6v (3.86 ave cell).
Charging data TO BE ADDED.

So it would appear that the lipo alarm should be set different for each type of battery I have. Is this normal or am I missing something?

[dirtyharry]

all depends on the lipo being used .  If I set my alarm to 3.7v per cell on the cheapo gens ace 1.3 25c batteries I use i';d only get 50% of the capacity out of them.  but the higher c rated ones drop off realy realy quickly so the 3.7v would be fine

Best bet is to set ur alarm to 3.6v as u have then see how much the charger squeezes back in , then adjust the alarm down to get 15-20% left and ur batteries should last.

[davethepitch]

Great thread Dave.

Hi Ched

You can rely on me to ask the most dumbest or the most obvious questions mate. 

Dave

[bazzerh]

higher C or just bigger packs in general will have less sagging under load and therefore you can set your alarm to a higher voltage knowing that the alarm will be giving your a truer reflection of the actual voltage.

smaller packs with low C ratings you';ll have to play around with the alarm so that its not going off on every blip of the throttle. i think i used to set mine at 3.3v when i first started and was using cheap zippy compacts. otherwise it would drive me nuts bleeping all the time. when the bleeping was constant at 3.3v setting then you';d know its time to come in. the packs voltage would usually pop back up to 3.6v ish after disconnecting.

setting 3.3v alarm for a high C pack wouldn';t be wise though as like others have said they drop off a cliff around there and if you were 100m out then the pack would suffer coming back in. 

[ched]

Hi Ched
You can rely on me to ask the most dumbest or the most obvious questions mate. 
Dave

It';s not a dumb question at all. I tried searching the net and there are lots of old stuff dating back upto 10 year. So more upto date thinking/experience is very helpful.
I was about to post a question about lipo alarm settings and found your post that was similar  ::)

So no question is dumb. The dumb question is the one you want an answer to and don';t ask!!!!

[davethepitch]

Just thought about something I have two Zippy 1800 mAh lipo';s one is 25C and the other is 35 C and I also have a Turnigy 1500 20-30 C lipo and I could do with a safe middle of the road value for my alarm.

Dave

[Gandhi]

I used to use lipo alarms, then got sick of losing them. Got annoyed with the beeper on the naze too. Nowadays, I set a timer on the taranis and use that. Start off with 4 mins for the first few flights and keep an eye on the voltage/amps put back in then increase accordingly.

Rarely do I over discharge a lipo. Even then, it';s likely cos I forgot to reset the flight timer and had to guesstimate.

[Friskle]

I used to use lipo alarms, then got sick of losing them. Got annoyed with the beeper on the naze too. Nowadays, I set a timer on the taranis and use that. Start off with 4 mins for the first few flights and keep an eye on the voltage/amps put back in then increase accordingly.

Rarely do I over discharge a lipo. Even then, it';s likely cos I forgot to reset the flight timer and had to guesstimate.

Im the same, timed a few flights, and do it that way, never used a voltage alarm on the model at all.

[Smit80]

As bazzerh alluded to earlier voltage on and off load makes a difference.

A lot of people never specify if their low limit is under load or not and old batteries will drop voltage more due to internal resistance.

Personally I take them close to 3.4v under load and remember old batteries will drop more as they age.

I had old onboard footage of my F550 when it was new only dropping 0.5v at 25Amp draw on a fully charged battery, 2 years later same battery dropping 1.3v..

[kilby]

Also the temperature will cause the battery to struggle

[Revs]

I always try to land at lowest 3.75v or ~15% charge remaining. I read that 3.3v under load is safe, though I have certain batteries showing 3.1v under load and seem to be lasting fine. If you';ve chosen your C rating correctly and your lipo is in good condition it';s only gonna be an issue under prolonged full throttle with a nearly dead lipo.

As said, the cold makes a huge difference. There';s no C rating high enough for winter. Just get a watt meter and keep an eye on them.

[gb0wers]

I aim for 3.7V recovered at rest post-flight and take in to account several factors to achieve this. On average I';m pumping about 1900 to 2000 mAh back in to a 2200 Hayin 20/30C 3S.

I have an alert set at 3.6V under load and reported by telemetry back to my Taranis,  but keep an eye on flight time and model position too. When doing low hover practice I get about 10 to 11 minutes before hitting 3.6V under load and can land in seconds so do not deplete the battery much following the alert. I';ve just started to FPV the quad and yesterday flying in higher wind than usual found that I';m getting less time to hit 3.6V, so must be driving it harder. I was higher and further away too, so took longer to land, resulting in a recovered rest voltage of 3.4V - lower than I';d like. I think I';ll try setting a LV alert to 3.7V and then an alarm at 3.6V.

[teslahed]

all depends on the lipo being used .  If I set my alarm to 3.7v per cell on the cheapo gens ace 1.3 25c batteries I use i';d only get 50% of the capacity out of them.  but the higher c rated ones drop off realy realy quickly so the 3.7v would be fine

Best bet is to set ur alarm to 3.6v as u have then see how much the charger squeezes back in , then adjust the alarm down to get 15-20% left and ur batteries should last.

This is the method I use because it usually works better than using voltage. Using voltage as an emergency backup to tell you if something is wrong still helps though (i.e if the battery alarm goes off early you';ve got a problem).

The fact that different batteries will drop voltage differently is also definitely a factor. When i first upgraded to turnigy nano-techs I destroyed a few by running them down to 3.3 volts like the zippy compacts I had used before. The zippys dropped voltage in use much more quickly so 3.3 was fine for them but it was killing the better nano-techs that only got that low after I';d drawn too many mAh.

Of course the best way to operate is to have a mAh counter that gives accurate mAh used in flight in real time. Tricky to setup though.